It looks as if it could be an Imperial Egg, the likes of which were given to royal family members back in the day, but it’s a Kelch Egg. The unseen initials B.K. (no, not Blood Killas, nor British Knights, nor Berkelium, nor Burger King) tell the story – they stand for Barbara (aka Varvara) Kelch:

“Every year from 1898 until 1904 Alexander Kelch ordered an Easter egg from Fabergé, modeled on the Imperial series, as a present for his wife, who no doubt also paid for them. No doubt, too, that the Kelch eggs cost them considerably more than those made for the Imperial family, given the parsimony of the Romanovs and the generosity of the nouveaux riches. The seven Kelch eggs are as fine, if not even more sumptuous, than those in the Imperial series.”

The Egg entered the Princely Collection of Monaco in 1974, as a gift to Prince Rainier III in honor of his Silver Jubilee — the 25th anniversary of his accession to the Grimaldi throne. The Blue Serpent Egg quickly became one of Princess Grace’s most treasured possessions, according to his Serene Highness Prince Albert II, son of Prince Rainier and Princess Grace. She adored it and kept it on the desk in her private study. After her tragic death in 1982, Prince Rainier sealed her suite, preserving the room as a memorial and thereby keeping the Blue Serpent Egg from public view.